Catgut, string made of the dried and twisted intestines of animals. Such strings are usually made from the intestines of sheep, but sometimes from those of the horse, ass, or mule. They are used on violins, harps, and other musical instruments, for the cords of bows, clocks, and whips, and for belting. They are prepared by first being freed from all feculent and fatty substances, then soaked and divested of the outside or peritoneal membrane by scraping, again soaked and the inner or mucous membrane taken away, and still further cleaned by the use of lye. They are next exposed to fumes of burning sulphur to purify them, and are slit and twisted into different sizes. They are then dyed, and afterward, as they are stretched upon frames, dried and hardened by exposure to a temperature of 180° to 200°. Lastly, they are cut off and coiled up for sale. Otto, in his " Treatise on the Violin," says that the best strings are those from Milan, sold by the name of Roman strings; and as these are imitated by inferior cords made in Bohemia and the Tyrol, he gives the following as the marks of the best article: "The Milanese strings are as clear and transparent as glass. The third string should be equally clean as the first.
They must by no means feel smooth to the touch, for they are not ground or polished off by any process, as all other manufactured strings are. If a good string be held by one end in the finger and opened out, it will recoil to its former position like a watch spring. Every string when stretched on the instrument should look like a thin strip of glass on the fingerboard; those which are of a dull and opaque appearance are useless. Their elasticity is after all the best criterion, as no other strings which I have tried have that strength and elasticity for which the Milanese are so much esteemed."